1. Technical Field
The present invention relates to a tandem-type image forming apparatus including a cleaner blade holding its distal end in contact against a surface of a moving transfer belt for cleaning the belt surface, and to an image forming method for the apparatus.
2. Related Art
A so-called tandem-type image forming apparatus is known as an image forming apparatus such as copiers, printers and facsimiles. JP A-2003-015378 is an example of related art. According to JP A-2003-015378, the tandem-type image forming apparatus includes a plurality of image forming stations arranged along the transfer belt transported in a predetermined direction, the image forming stations individually forming toner images of mutually different colors. Such an image forming apparatus forms a color image by superimposing the toner images on the surface of the transfer belt, the toner images formed by the respective image forming stations in mutually different colors. The color image formed on the belt surface is transferred to a transfer medium such as paper.
In some cases, such an image forming apparatus may be provided with the cleaner blade for removing toner remaining on the surface of the transfer belt. Such a cleaner blade holds its distal end in contact against the surface of the transfer belt transported in the predetermined direction, thereby removing the residual toner from the transfer belt surface.
Besides the above residual toner, however, contaminant such as powdery paper may sometimes adhere to the surface of the transfer belt. Similarly to the residual toner, the contaminant may be mostly removed from the transfer belt surface by means of the cleaner blade. However, some of the contaminant may sometimes adhere to the distal end of the cleaner blade so as to be caught between the distal end of the cleaner blade and the transfer belt surface. As a result, a clearance is formed between the cleaner blade and the transfer belt surface, so that an adequate removal of the residual toner may not be achieved because the residual toner is allowed to pass through the clearance.
JP A-2004-102178, for example, also points out the aforementioned problem encountered by the constitution wherein the cleaner blade is pressed against an image carrier such as the transfer belt moved in the predetermined direction, thereby cleaning the surface of the image carrier. According to JP A-2004-102178, a rotational direction of the image carrier is controlled to overcome the above problem. Specifically, the image carrier is rotated in the opposite direction of a direction in which the image carrier is rotated during the image formation. The image carrier is driven in the opposite direction for moving the contaminant caught between the surface of the image carrier and the distal end of the cleaner blade to an upstream side of the rotational direction for image formation, whereby the contaminant is separated from the distal end of the cleaner blade.